AES Lecture 1 - Introduction

7/29/2019 AES Lecture 1 - Introduction

1/20

Automotive Electrical Syste

BTAE 404

Recommended Books:

1) Kohli P.L., Automotive Electrical Equipment ", Tata McGraw-Hill.

2) W.H. Crouse, Automobile Electrical Equipment ", McGraw Hill Book Co. Inc.

1) C.P.Nakra, Basic Automotive Electrical Systems, Dhanpat Rai and sons

Lecture by :

Jagwant SinghAssistant Professor

Department of Automobile Engineering

Gulzar College of Engineering , Khanna


2/20

Lecture 1

Introduction to

Automotive Electric Systems


3/20

Introduction

Current and Voltage are two different but related aspects of electricity.Voltage is the electrical potential difference between two points while

current is the rate of flow of electric charge across a certain element.

OHMs Law:

Ohm's law states that the current through a conductor between two points is

directly proportional to the potential difference across the two points.

V=IR


4/20

HT Leads

High tension leads or high tension cables (or spark plug wires or spark plugcables) are the wires that connect a distributor and ignition coil to each of the

spark plugs in some types of internal combustion engine.

"High tension lead" or "cable" is also used for any electrical cable carrying a high

voltage .


5/20

HT Leads


6/20

Insulated Return Systems As Shown in figure , Connections for the Lamp and Battery with Feed wire and

return wire

The RED wire is called Feed Wire . To Complete the circuit , the Black cable

joining the lamp to the battery acts as a return for the Supply Current

The Term insulated return is used whenever an insulated cable provides thereturn path for the current.


7/20

Earth Return System

In this case the vehicle frame provides the return path for the current


8/20

Earth Return System

Advantages of this system are :

Reduced cost

Lighter weight of wires

Simpler Circuit Layout

Extra Precautions must be taken with this system to prevent cutting of feed

wire rubber insulation by a sharp part of the vehicles frame or body, if thisoccurs the supply current will be conducted to body so, A fire can be started

Most of the vehicles have an earth return system , the exceptions are thespecial purpose vehicles such as petrol tankers that have a high fire risk, that

use the insulated return system


9/20

Earth Polarity

Earth polarity means that which pole of battery or Electrical system isconnected to body of vehicle (to ground).

In Case , Negative Terminal of the battery connected to the frame , thatarrangement is called Negative Earth system.

This is Commonly used on the majority of modern vehicles

However , some older cars were built with a "positive earth" electrical system, in

this case the positive terminal of the battery is bonded to the chassis and thenegative terminal for the live.


10/20

Negative earth was adopted globally by automobile manufacturers for thesake of standardization.

It was due to the introduction of radios in automobiles that may have seennegative earth automobiles being favored.

It was also that positive earth vehicles rusted quicker (Cathode Sacrificial

Protection).


11/20

Circuit Faults

Failure of electrical system is often caused by a circuit fault . Two common faultsare considered are :

Open Circuit

Short Circuit


12/20

Open Circuit

A complete enclosed Circuit is needed if current is to flow around the system.

An open circuit exists when the circuit is interrupted either intentionally or

un-intentionally may be due to Wire breakage


13/20

Short Circuit

When the feed or switch wire insulation is damaged and the conductor wiretouches the metal frame , which is negative .All the current will take this

easy path to return to battery .

This alternative path offers the current a short path back to battery , so the

term Short Circuit is used to describe this condition.

This short path have very low resistance . When short circuit occurs the very

high current flow ( because no current is consumed in other work ,so all the batterycurrent return back to battery)That results will soon make the cable glow Red-Hot . This melts the plastic covering of the cable and often starts a fire .

Some circuit-protection devices such as a fuse is needed if this danger is

to be avoided


14/20

Fuse

Fuse is a type of low resistance wire that acts as a sacrificial device toprovide overcurrent protection, of either the load or source circuit.

Its essential component is a metal wire or strip that melts when too muchcurrent flows, which interrupts the circuit in which it is connected.

Short circuit, overloading, mismatched loads or device failure are the prime

reasons for excessive current

Fig: Fuse Symbols


15/20

Automotive Fuses

Automotive fuses are a class of fuses used to protect the wiring and electricalequipment for vehicles. They are generally rated for circuits no higher than

24 volts direct current

Types

Blade type

Bosch type

Lucas type

Glass Tube type

Limiter type


16/20

Blade type Fuse

Blade fuses (also called spade or plug-in fuses), with a plastic body and twoprongs that fit into sockets, are mostly used in automobiles. Each fuse is

printed with the Rated Current in Amperes on the top.

These types of fuses come in four different physical dimensions:

Low-profile mini (APS / Micro)

Mini (APM / ATM)

Regular (APR / ATC / ATO)

Maxi (APX) heavy-duty.


17/20

Blade type FuseSize Groups

Blade Size Blade GroupDimensions L W

HCommon Ratings

Low-Profile Mini APS, ATT10.9 3.81 8.73

mm

2, 5, 7.5, 10, 15,

20, 25, 30

Mini APM, ATM10.9 3.6 16.3

mm

2, 3, 4, 5, 7.5, 10,

15, 20, 25, 30

RegularAPR, ATC (Closed),ATO (open)

19.1 5.1 18.5mm

1, 2, 3, 4, 5, 7.5,10, 15, 20, 25, 30,35, 40

Maxi APX29.2 8.5 34.3

mm

20, 25, 30, 35, 40,50, 60, 70, 80,

100, 120


18/20

Bosch type Fuse

Bosch type fuses (also known as torpedo, ATS, or GBC type fuses) are used inold automobiles.

The physical dimension of this type of fuse is 625 mm with conical ends.Bosch type fuses usually use the same color coding for the rated current

Color Ampere

Yellow 5

White 8

Red (or Green) 16

Blue 25

Grey 40

Color coding
http://en.wikipedia.org/wiki/Amperehttp://en.wikipedia.org/wiki/Ampere


19/20

Lucas type Fuse

Lucas type fuses are used in old British-made or assembled automobiles. Thephysical length of this ceramic type of fuse is either 1 inch or 1.25 inch, with

conical ends.


20/20

Glass Tube type Fuse

North-American built old automobiles had electrical systems protected byglass cartridge fuses rated 32 volts and current ratings from 4 amperes to 30

amperes. The fuse dimensions and characteristics are standardized by the

Society of Automotive Engineers standard J554. All fuses are 1/4 inchdiameter, and the length varies according to the rating of the fuse. A 4 Amp

fuse is 5/8 of an inch long, a 20 Amp fuse is 1 inches long, and a 30 ampfuse is 1716 inches long.

Documents

AES Lecture 1 - Introduction